Activating and deactivating sensors for dead reckoning

ABSTRACT

An identification is made as to when a device is at an anchor location, which can be a proximity zone along an edge of a dead zone or a location where a signal from a beacon is detected. In response to the device being at the anchor location, one or more inertial sensors can be activated and data from the one or more inertial sensors collected to determine a position of the device using dead reckoning. Alternatively, in response to the device being at the anchor location, a determination is made as to when to deactivate one or more inertial sensors from which data is collected to determine the position of the device using dead reckoning.

BACKGROUND

As cellular phones have become more commonplace and powerful, the desirefor certain applications to provide location-based functionality onthese phones has increased. In order to provide such location-basedfunctionality, the position of the phone needs to be known. The positionof a phone can sometimes be determined based on coordinates receivedfrom a global positioning system (GPS) of the phone. However, it remainsdifficult to determine the position of a phone under certaincircumstances, such as when the GPS of the phone is not able todetermine an accurate position of the phone, or when the phone does notinclude GPS functionality.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

In accordance with one or more aspects, an identification is made that adevice is at an anchor location. In response to the device being at ananchor location, one or more inertial sensors are activated. Data fromthe one or more inertial sensors is collected to determine a position ofthe device using dead reckoning.

In accordance with one or more aspects, an identification is made that adevice is at an anchor location. Based at least in part on the devicebeing at the anchor location, a determination is made as to when todeactivate one or more inertial sensors from which data is collected todetermine the position of the device using dead reckoning.

BRIEF DESCRIPTION OF THE DRAWINGS

The same numbers are used throughout the drawings to reference likefeatures.

FIG. 1 illustrates an example system implementing the activating anddeactivating of sensors for dead reckoning in accordance with one ormore embodiments.

FIG. 2 illustrates an example user interface that can be displayed to auser of a device to allow the user to select whether position data forthat device will be recorded and provided to a crowd sourcing dataservice in accordance with one or more embodiments.

FIG. 3 illustrates an example device implementing the activating anddeactivating of sensors for dead reckoning in accordance with one ormore embodiments.

FIG. 4 illustrates an example proximity zone in accordance with one ormore embodiments.

FIG. 5 illustrates an example use of anchored beacons in accordance withone or more embodiments.

FIG. 6 illustrates an example use of backtracking in accordance with oneor more embodiments.

FIG. 7 is a flowchart illustrating an example process for crowd sourcingbased on dead reckoning in accordance with one or more embodiments.

FIG. 8 is a flowchart illustrating an example process for activating anddeactivating inertial sensors for dead reckoning in accordance with oneor more embodiments.

FIG. 9 illustrates an example computing device that can be configured toimplement the activating and deactivating of sensors for dead reckoningin accordance with one or more embodiments.

DETAILED DESCRIPTION

Activating and deactivating sensors for dead reckoning is discussedherein. A device identifies signals it receives at a particular point intime, such as Wi-Fi signals and cell tower signals. The device recordsdata indicating these identified signals, as well as data indicating theposition of the device at that particular point in time. The position ofthe device can be determined using a Global Navigation Satellite System(GNSS) such as GPS. In situations in which a GNSS is not available ordoes not provide an accurate enough position, dead reckoning can be usedto determine the position of the device. The position determined usingdead reckoning can also be modified based on signals received frombeacons anchored at known positions. The ability to determine theposition of the device is thus extended into areas in which a GNSS isnot available or does not provide an accurate enough position. When theposition of the device is determined using dead reckoning variousinertial sensors can be activated, and these inertial sensors can bedeactivated at other times to conserve energy.

The device records data indicating the identified signals and positionof the device at various times, as do other devices, and the recordeddata is provided by these devices to a collection system. This dataprovided by the devices, also referred to as crowd sourcing data, iscollected by the collection system and can subsequently be used in anyof a variety of different manners.

FIG. 1 illustrates an example system 100 implementing the activating anddeactivating of sensors for dead reckoning in accordance with one ormore embodiments. System 100 includes one or more (m) devices 102 thatcan communicate with a crowd sourcing data service 104 via a network106. Network 106 can be a variety of different networks, including theInternet, a local area network (LAN), a wide area network (WAN), atelephone network, an intranet, other public and/or proprietarynetworks, combinations thereof, and so forth.

Each device 102 can be a variety of different types of devices, withdifferent devices 102 being the same or different types of devices.Device 102 is typically a mobile device, the position of which isexpected to change frequently over time. For example, device 102 can bea cellular or other wireless phone, a laptop or netbook computer, atablet or notepad computer, a mobile station, an entertainmentappliance, a game console, an automotive computer, and so forth. Thus,device 102 may range from a full resource device with substantial memoryand processor resources (e.g., personal computers, game consoles) to alow-resource device with limited memory and/or processing resources(e.g., traditional set-top boxes, hand-held game consoles).

Device 102 records data identifying signals that device 102 receives anda corresponding position of device 102 at various points in time, asdiscussed in more detail below. Device 102 can also optionally providevarious other functionality in addition to recording the dataidentifying received signals and corresponding device position atvarious points in time, such as a phone functionality, automotivecomputer functionality, gaming functionality, and so forth.Alternatively, device 102 can be a dedicated position sensing devicethat supports little, if any, functionality other than recording thedata identifying received signals and corresponding device position atvarious points in time.

Each device 102 includes a crowd sourcing module 108 that supports deadreckoning. Each crowd sourcing module 108 can use dead reckoning todetermine the position of the device 102 including that module 108, asdiscussed in more detail below. Although illustrated as a single module,it should be noted that the functionality of module 108 canalternatively be separated into multiple modules. Data indicating thisdetermined position of the device 102, as well as data identifyingsignals received by the device 102 (and optionally strengths of thosesignals) at that determined position, at various times is recorded bydevice 102. This recorded data is also referred to as crowd sourcingdata, and is provided to crowd sourcing data service 104. Crowd sourcingas used herein refers to each of multiple (typically a large number,such as hundreds of thousands or more) devices providing data to aservice, so the service obtains data from a crowd of devices rather thanrelying on data from a single device. Both the individual devices andthe service play a part in the crowd sourcing.

Crowd sourcing data service 104 receives recorded data from multipledevices 102, collecting the data for subsequent use. The data collectedby crowd sourcing data service 104 can be used to provide variouslocation-based or position-based functionality. As used herein, alocation refers to a general or larger geographic area rather than aprecise coordinate, such as one or more buildings (e.g., home or work),a business or store, a buffer zone around a building, and so forth. Aposition, however, refers to a geographic area that is more precise thana location, such as a coordinate in some coordinate system (e.g., aparticular latitude and/or longitude), a particular elevation, and soforth. Thus, each location can include multiple positions. Crowdsourcing data service 104 is implemented using one or more devices. Theone or more devices used to implement crowd sourcing data service 104can be a variety of different types of devices, such as servercomputers, desktop computers, any of the various types of devicesdiscussed above with reference to device 102, and so forth. Service 104can be implemented using multiple ones of the same and/or differenttypes of devices.

In one more embodiments, the recording of data indicating the positionof a device and/or the providing of the recorded data to crowd sourcingdata service 104 is performed only after receiving user consent to doso. This user consent can be an opt-in consent, where the user takes anaffirmative action to request that the position data be recorded beforecrowd sourcing module 108 performs any recording of data for the device.Alternatively, this user consent can be an opt-out consent, where theuser takes an affirmative action to request that the position data notbe recorded; if the user does not choose to opt out of this recording ofthe position data, then it is an implied consent by the user to recordthe position data.

Furthermore, it should be noted that the activating and deactivating ofsensors for dead reckoning techniques discussed herein can allow devices102 to provide position data to crowd sourcing data service 104, butneed not include any personal information identifying particular usersof devices 102 and/or particular devices 102. For example, a device 102can record position data and provide the position data to service 104,but no association between the device 102 and the position data need beprovided to and/or maintained by service 104. Similarly, no associationbetween the user of the device 102 and the position data need beprovided to and/or maintained by service 104.

FIG. 2 illustrates an example user interface that can be displayed to auser of a device to allow the user to select whether position data forthat device will be recorded and provided to a crowd sourcing dataservice in accordance with one or more embodiments. A position recordingcontrol window 200 is displayed including a description 202 explainingto the user why the position of the device is being recorded. A link 204to a privacy statement is also displayed. If the user selects link 204,a privacy statement is displayed, explaining to the user how therecorded position data is kept confidential and/or how no associationbetween the position and the device (as well as the user of the device)is maintained.

Additionally, the user is able to select a radio button 206 to opt-in tothe position recording, or a radio button 208 to opt-out of the positionrecording. Once a radio button 206 or 208 is selected, the user canselect an “OK” button 210 to have the selection saved. It is to beappreciated that radio buttons and an “OK” button are only examples ofuser interfaces that can be presented to a user to opt-in or opt-out ofthe position recording, and that a variety of other conventional userinterface techniques can alternatively be used. The device then proceedsto record or not record the device position in accordance with theuser's selection.

FIG. 3 illustrates an example device 300 implementing the activating anddeactivating of sensors for dead reckoning in accordance with one ormore embodiments. Device 300 can be, for example, a device 102 ofFIG. 1. Device 300 includes a Global Navigation Satellite System (GNSS)module 302, a Wi-Fi module 304, a communications module 306, an inertialsensor module 308, a data collection module 310, a backtracking module312, a position determination module 314, a dead reckoning positionmodule 316, a data transfer module 318, and a data store 320. Modules302-318 can implement, for example, crowd sourcing module 108 of FIG. 1.Each module 302-318 can be implemented in software, firmware, hardware,or combinations thereof. Although specific modules are illustrated inFIG. 3, it should be noted that additional modules can be included indevice 300 and/or some modules (e.g., backtracking module 312)illustrated need not be included in device 300. Additionally, it shouldbe noted that the functionality of multiple modules illustrated in FIG.3 can be combined into a single module, and/or the functionality of oneor more modules illustrated in FIG. 3 can be separated into multiplemodules.

GNSS module 302 implements GNSS functionality for device 300,determining a position of device 300 based on one or more satellitesfrom which GNSS module 302 can receive signals or otherwise communicate.This determined position is typically latitude and longitudecoordinates, although the position can alternatively be specified inother manners. GNSS module 302 can implement the GNSS functionalityusing a variety of different technologies, such as the GlobalPositioning System (GPS), the Global Navigation Satellite System(GLONASS), the BeiDou (or Compass) navigation system, the Galileopositioning system, combinations thereof, and so forth.

GNSS module 302 provides or otherwise makes available the determinedposition of device 300 to various other modules of device 300. GNSSmodule 302 can also provide or otherwise make available an indication ofan estimate of the accuracy of the position of device 300 determined byGNSS module 302. For example, GNSS module 302 can indicate that aparticular determined position of device 300 is estimated to be accurateto within a particular distance (e.g., 3 meters or 8 meters). By way ofanother example, GNSS module 302 can indicate that a particular positionof device 300 was determined based on signals received from a particularnumber of satellites (e.g., 3 satellites or 7 satellites), can indicatethe strength of signals received by module 302 from satellites, and soforth. Based on such an indication, another module of device 300 candetermine an estimated accuracy of the determined position (e.g.,estimated to be accurate within 40 meters if signals are received from 3satellites, and within 8 meters if signals are received from 7satellites).

GNSS module 302 can determine the position of device 300 at regular orirregular intervals. GNSS module 302 can also determine the position ofdevice 300 in response to various events, such as a request from anothermodule of device 300. In one or more embodiments, GNSS module 302 canalso be deactivated or powered down at various times (e.g., to conserveenergy), and not determine the position of device 300 until module 302is activated or powered on. GNSS module 302 can be configured todeactivate or power down itself in response to certain conditions (e.g.,receiving signals from fewer than a threshold number of satellites for athreshold amount of time), and/or in response to a deactivate or powerdown signal from another module of device 300. GNSS module 302 can beactivated or powered on in response to a signal from another module ofdevice 300 and/or in response to certain conditions (e.g., beingdeactivated or powered down for a threshold amount of time).

Wi-Fi module 304 implements wireless functionality for device 300,sending signals to and/or receiving signals from devices on variouswireless networks. Wi-Fi module 304 can receive signals from variouswireless access points, including an identifier of a particular wirelessaccess point and/or a particular wireless network from which a signal isreceived. For example, a wireless access point may send a media accesscontrol (MAC) address of the wireless access point, a basic service setidentifier (BSSID) of a wireless network supported by the wirelessaccess point, and so forth. Wi-Fi module 304 also measures a strength(e.g., received signal strength indicator (RSSI) values) of thesereceived radio signals. It should be noted that Wi-Fi module 304 can, atany given time for any given position of device 300, receive signalsfrom multiple wireless access points. Wi-Fi module 304 provides orotherwise makes available an indication of the identifiers of theparticular wireless access points and/or wireless networks from whichsignals are received, as well as the strengths of those signals, tovarious other modules of device 300.

Wi-Fi module 304 can detect particular wireless access points and/orwireless networks from which signals are received, and the strength ofthose signals, at regular or irregular intervals. Wi-Fi module 304 canalso detect particular wireless access points and/or wireless networksfrom which signals are received, and the strength of those signals, inresponse to various events, such as a request from another module ofdevice 300.

Communications module 306 implements cell phone functionality for device300, sending signals to and/or receiving signals from various celltransceivers (e.g., cell towers). Communications module 306 can receivesignals from various cell transceivers, including an identifier of aparticular cell transceiver (e.g., a cell tower or transceiveridentifier) from which a signal is received. Communications module 306also measures a strength (e.g., RSSI values) of these received signals.It should be noted that communications module 306 can, at any given timefor any given position of device 300, receive signals from multiple celltransceivers. Communications module 306 provides or otherwise makesavailable an indication of the identifiers of the particular celltransceivers from which signals are received, as well as the strengthsof those signals, to various other modules of device 300.

Communications module 306 can detect particular cell transceivers fromwhich signals are received, and the strength of those signals, atregular or irregular intervals. Communications module 306 can alsodetect particular cell transceivers from which signals are received, andthe strength of those signals, in response to various events, such as arequest from another module of device 300.

Inertial sensor module 308 includes one or more inertial sensors thatdetect movement (e.g., rotation, motion, velocity, etc.), position, ordirection. These inertial sensors can be MEMS (MicroelectromechanicalSystems or Microelectronicmechanical systems). These inertial sensorscan include, for example, an accelerometer, a compass, a gyroscope, abaroaltimeter, and so forth. Inertial sensor module 308 collects dataregarding the detected movement, position, and/or direction of device300 from these inertial sensors, and provides or otherwise makesavailable this collected data to other modules of device 300. This datacan be used to determine a position of device 300 using dead reckoning,as discussed in more detail below.

It should also be noted that although inertial sensor module 308 isillustrated as being part of device 300, one or more inertial sensorscan be implemented as a separate component or device that is coupled todevice 300. For example, inertial sensors can be implemented as part ofa watch worn by a user, as part of a device attached to a user's shoe,as part of a heart rate monitor component, and so forth.

Inertial sensor module 308 can collect data at regular or irregularintervals. Inertial sensor module 308 can also collect data in responseto various events, such as a request from another module of device 300.In one or more embodiments, inertial sensor module 308 (including theinertial sensors) can also be deactivated or powered down at varioustimes (e.g., to conserve energy), and not provide or collect data untilmodule 308 is activated or powered on. Inertial sensor module 308 can beconfigured to deactivate or power down itself in response to certainconditions (e.g., after a threshold amount of time), and/or in responseto a deactivate or power down signal from another module of device 300.Inertial sensor module 308 (including the inertial sensors) can beactivated or powered on in response to a signal from another module ofdevice 300 and/or in response to certain conditions (e.g., beingdeactivated or powered down for a threshold amount of time).

Dead reckoning position module 316 determines the position of device 300based on data collected by inertial sensor module 308. Dead reckoningrefers to determining a position of device 300 based on the movement ofdevice 300 (e.g., as opposed to receiving one or more signals indicatingthe position of device 300). In device 300, the movement of device 300is indicated by the data collected from the inertial sensors asdiscussed above. The dead reckoning is performed based on a knownstarting position (e.g., a position determined by GNSS module 302, aposition identified by a beacon as discussed below, a position specifiedby a user of device 300 (e.g., by providing a user input of the positionon a map), etc.). Dead reckoning position module 316 analyzes the datacollected from the inertial sensors using a variety of differentconventional and/or proprietary algorithms, rules, or criteria todetermine, based on the known starting position and movement of device300, the position of device 300 at a particular time.

The position of device 300 determined based on the inertial sensors issubject to a particular error over time and/or movement, referred to asdrift. This error typically accumulates over time and/or movement,increasing as time elapses and/or the distance moved increases. Deadreckoning position module 316 can determine an estimate of the accuracyof the position of device 300 determined based on the data from inertialsensor module 308. Various conventional and/or proprietary algorithms,rules, or criteria can be used to determine the estimated error. Forexample, dead reckoning position module 316 can determine that, aftermovement of a threshold distance is detected, the estimated error in thedetermined position of device 300 is a particular number of meters(e.g., the estimated error may be 3 meters after walking 400 meters).

Position determination module 314 implements functionality to determinethe position of device 300. This position is typically latitude andlongitude coordinates, although the position can alternatively bespecified in other manners. Position determination module 314 candetermine the position of device 300 to be the position determined byGNSS module 302 as discussed above, or the position determined by deadreckoning position module 316 as discussed above. Position determinationmodule 314 automatically determines whether the position of device 300at any given time is the position determined by GNSS module 302 or theposition determined by dead reckoning position module 316 based onvarious factors, as discussed in more detail below. It should be notedthat position determination module 314 automatically determines whetherto use the position determined by module 302 or the position determinedby module 316—no action on the part of a user of device 300 need beperformed to switch between modes or otherwise select one of modules 302or 316 to provide the position for position determination module 314.

Data collection module 310 implements functionality to record dataidentifying signals that device 300 receives and a correspondingposition of device 300 at various points in time. Wi-Fi module 304provides or otherwise makes available an indication of the identifiersof the particular wireless access point and/or wireless network fromwhich signals are received, as well as the strengths of those signals,as discussed above. Communications module 306 provides or otherwisemakes available an indication of the identifiers of the particular celltransceivers from which signals are received, as well as the strengthsof those signals, as discussed above. The indication of the identifiersof the particular wireless access point and/or wireless network fromwhich signals are received at a particular point in time (as well as thestrengths of those signals) and/or the indication of the identifiers ofthe particular cell transceivers from which signals are received at thatparticular point in time (as well as the strengths of those signals) isalso referred to as observation data at that particular point in time.Data collection module 310 records, in data store 320, the observationdata at that particular point in time. A position of device 300 (asdetermined by position determination module 314) at that particularpoint in time is also recorded in data store 320 and corresponds to theobservation data.

Data collection module 310 stores a record including the observationdata and corresponding position of device 300 at different points intime. These different points in time can be at regular intervals,irregular intervals, or can be determined based on other factors orevents. However, over time, data collection module 310 stores multiplesuch records in data store 320.

Data transfer module 318 sends the recorded observation data andcorresponding positions to a data service (e.g., crowd sourcing dataservice 104 of FIG. 1). Data transfer module 318 can send the recordedobservation data and corresponding positions to the data service atregular or irregular intervals, or alternatively in response to otherevents (e.g., device 300 being connected to or logged into a particularnetwork).

Position determination module 314 can determine the position of device300 using GNSS module 302 and/or dead reckoning position module 316.Each module 302 and 316 has an estimated accuracy for the position ofdevice 300 determined by that module. Position determination module 314can determine the estimated accuracy for the position of device 300 frommodule 302 and/or module 316 as the estimated accuracy provided bymodule 302 and/or module 316, and/or determine the estimated accuracyfor the position of device 300 based on data provided by module 302and/or module 316.

Generally, position determination module 314 determines as the positionof device 300 the position determined by GNSS position module 302 untildevice 300 is detected as being at one of one or more anchor locations.An anchor location indicates to device 300 to get ready to use deadreckoning for position determination, for example because the estimatedaccuracy of GNSS module 302 may decrease and/or GNSS module 302 may beunable to determine a position of device 300 soon (e.g., within athreshold amount of time, such as within the next few or severalseconds). Position determination module 314, in response to determiningthat device 300 is at an anchor location, activates or powers oninertial sensor module 308 if module 308 is not already activated orpowered on. Module 314 determines the estimated accuracy of the positionof device 300 as determined by module 302 and the estimated accuracy ofthe position of device 300 as determined by module 316, and determinesas the position of device 300 the one of the two determined positions(from module 302 or 316) that is more accurate (e.g., is estimated to beaccurate within a smaller amount). For example, if one determinedposition is estimated to be accurate within 8 meters and the otherposition is estimated to be accurate within 40 meters, the positionestimated to be accurate within 8 meters is the more accurate of the twopositions

It should be noted that inertial sensor module 308 (including theinertial sensors) can be typically deactivated or powered down, and thenactivated or powered on when device 300 is detected as being at ananchor location. When deactivated or powered down, inertial sensorsincluded in module 308 consume very little if any energy. Thus, bykeeping inertial sensor module 308 deactivated or powered down until atan anchor location (and using as the position of device 300 the positiondetermined by GNSS module 302), the energy usage of device 300 can bereduced. However, inertial sensor module 308 can then be activated orpowered on to provide data used to determine the position of device 300when the estimated accuracy of GNSS module 302 may decrease and/or GNSSmodule 302 may be unable to determine a position of device 300 soon.

The anchor locations can be specified in various manners. In one or moreembodiments, the anchor locations are locations along the edge orperimeter of a dead zone, these locations being referred to as aproximity zone. A dead zone as used herein refers to an area in whichGNSS module 302 cannot provide a position deemed to be accurate enough.For example, a dead zone can be an area in which the estimated accuracyof the position determined by GNSS module 302 is below a thresholdamount, an area in which GNSS module 302 is unable to determine aposition, an area in which signals are received from less than athreshold number of satellites, combinations thereof, and so forth.

The proximity zone can be defined in various manners. In one or moreembodiments, position determination module 314 has access to a mappingof (e.g., latitude and longitude coordinates of) dead zones. Theproximity zones can be determined based on the dead zones in a varietyof different manners. In one or more embodiments, the proximity zonesare specified as a particular distance or buffer space extending awayfrom the edge of the dead zone. For example, the proximity zones can bethe area that is a 5-meter buffer along the edge of the dead zone. Theparticular distance or buffer space can be based on various factors,such as the amount of time inertial sensor module 308 takes to provideaccurate data after being activated or powered on, an expected speed ofdevice 300, and so forth.

Alternatively, the proximity zones can be specified as a particulardistance or buffer space extending away from the edge of the dead zonewithin a particular distance of an entrance to the dead zone. Forexample, the proximity zone can be the area that is both a 5-meterbuffer along the edge of the dead zone and within 5 meters of anentrance to the dead zone (e.g., within two meters of a door to abuilding that is a dead zone).

The proximity zones can be fixed, such as a 5-meter buffer along theedge of the dead zone. Alternatively, the proximity zones can bevariable, changing based on the speed of device 300. Positiondetermination module 314 can readily determine the speed of device 300based on determined positions of device 300 (e.g., by GNSS module 302)and the time between those determinations. The proximity zone canincrease as the speed of device 300 increases, and decrease as the speedof device 300 decreases. For example, the proximity zone when device 300is being held by a user that is running may be a 10-meter buffer alongthe edge of the dead zone, and the proximity zone when device 300 isbeing held by a user that is walking slowly may be a 3-meter bufferalong the edge of the dead zone.

Given the proximity zones, position determination module 314 can readilydetermine when device 300 is in a proximity zone based on the positionof device 300 as determined by GNSS module 302. The mapping of proximityzones can be obtained in different manners, such as from data store 320or other store of device 300, from a device or service external todevice 300, and so forth.

FIG. 4 illustrates an example proximity zone in accordance with one ormore embodiments. A dead zone 402 is illustrated in FIG. 4 as the areawith cross-hatching. A proximity zone 404 surrounding dead zone 402 isshown as the area between dead zone 402 and dashed line 406.Additionally, an open area 410 is illustrated that is excluded from, butsurrounded by, dead zone 402. In open area 410, the estimated accuracyof the position determined by GNSS module 302 is not below a thresholdamount, and thus open area 410 is not included in dead zone 402. Openarea 410 could be, for example, an area below skylights in a building,or an outdoor courtyard surrounded by a building. A proximity zone 412around the edge of dead zone 402 (the edge between dead zone 402 andopen area 410) is shown as the area between dead zone 402 and dashedline 414.

Returning to FIG. 3, anchor locations can alternatively be specified inother manners. For example, the anchor locations can be locationsspecified by a user of device 300 (e.g., by providing a user input ofthe location on a map), etc.). By way of another example, the anchorlocations can be locations where a signal from a beacon is detected.Beacons can be implemented in a variety of different manners, such asBluetooth transmitters, Bluetooth Low Energy (BLE) transmitters, radiofrequency transmitters, Near Field Communication (NFC) transmitters, andso forth. Each such beacon can transmit a signal that is detected byposition determination module 314, and can include an indication thatthe beacon is a beacon for an anchor location and/or an indication ofthe position of the beacon. The position of the beacon can betransmitted in different manners, such as being transmitted as latitudeand longitude coordinates, being transmitted as an identifier that canbe looked up in a table accessible to module 314 to determine acorresponding position of the beacon, and so forth. Beacons aretypically located at the edge or perimeter of a dead zone (e.g., withinor near (within a threshold distance of) a dead zone) where a user canmove between the dead zone and a non-dead zone, and optionally can belocated elsewhere (e.g., within a dead zone).

FIG. 5 illustrates an example use of anchored beacons in accordance withone or more embodiments. A dead zone 502 is illustrated in FIG. 5 as thearea with cross-hatching, analogous to dead zone 402 of FIG. 4.Additionally, an open area 510 is illustrated that is excluded from, butsurrounded by, dead zone 502, analogous to open area 410 of FIG. 4.Multiple beacons 520, 522, 524, 526, and 528 are illustrated. Eachbeacon 520-528 transmits a signal for a particular radius around thebeacon (e.g., a 3-meter radius). Although the beacons 520-528 areillustrated as transmitting signals having the same radius, it should benoted that the radius of signals transmitted by different beacons can bedifferent. Additionally, although the beacons 520-528 are illustrates astransmitting a signal with a constant radius in all directions from thebeacons, the transmitted signal from a beacon can have a differentradius in different directions. For example, a beacon may be mounted toa wall and transmit a signal with a 3-meter radius in a direction awayfrom the wall, and a 1-meter radius in a direction towards the wall.

Returning to FIG. 3, position determination module 314 determines theposition of device 300 using GNSS module 302 and/or dead reckoningposition module 316 while the estimated accuracy of the positiondetermined by at least one of module 302 and module 316 remainsacceptable. Whether the estimated accuracy of the position determined byat least one of module 302 and module 316 is acceptable can bedetermined in different manners, such as based on a particular estimatedaccuracy that position determination module 314 is configured to use.Module 314 can be configured with this particular estimated accuracy indifferent manners, such as being pre-configured in module 314, being setby a user of device 300, being obtained from another source, and soforth. If the estimated accuracy of the position determined by at leastone of module 302 and module 316 satisfies (e.g., is less than or equalto) the particular estimated accuracy, then the estimated accuracy ofthe position determined by at least one of module 302 and 316 isacceptable. However, if the estimated accuracy of the positiondetermined by at least one of module 302 and module 316 does not satisfy(e.g., is not less than or equal to) the particular estimated accuracy,then the estimated accuracy of the position determined by at least oneof module 302 and 316 is not acceptable.

Typically, as device 300 is moved into a dead zone, dead reckoningposition module 316 determines a position of device 300 with a better(more accurate) estimated accuracy than GNSS module 302 determines fordevice 300. When comparing estimated accuracies, smaller values aretypically better estimated accuracies (e.g., an estimate of beingaccurate within 3 meters is better than an estimate of being accuratewithin 8 meters), although depending on the manner in which estimatedaccuracies are specified larger or other values can be better estimatedaccuracies. Thus, as device 300 is moved into a dead zone, positiondetermination module 314 typically determines as the position of device300 the position determined by dead reckoning position module 316 untilthe module 316 no longer provides an acceptable estimated accuracy(e.g., due to drift as discussed above). This duration for which deadreckoning position module 316 provides an acceptable estimated accuracyis also referred to as a dead reckoning fidelity interval.

It should also be noted that beacons can optionally be placed at variouspositions within a dead zone. A variety of different types of beaconscan be used, analogous to the discussion above regarding anchorlocations. Position determination module 314 can identify these beaconsand dead reckoning position module 316 can use the position identifiedby such a beacon as the known starting position of device 300 for deadreckoning. For example, the inertial sensors can be reset (e.g., turnedoff and back on) to use the position identified by the beacon as theknown starting position of device 300. Dead reckoning position module316 can then continue to determine, based on data from inertial sensormodule 308, the position of device 300 from the position identified bythe beacon (analogous to module 302 determining the position of device300 from an anchor location). The dead reckoning fidelity interval canthus effectively be extended each time such a beacon is encountered.

Situations can arise in which neither GNSS module 302 nor dead reckoningposition module 316 determine a position of device 300 with anacceptable estimated accuracy. In such situations, data collectionmodule 310 can optionally stop recording the observation data and thecorresponding position of device 300. If at a later time at least one ofGNSS module 302 and dead reckoning position module 316 determines aposition of device 300 with an acceptable estimated accuracy, datacollection module 310 resumes recording the observation data and thecorresponding position of device 300.

Alternatively, data collection module 310 can continue to record theobservation data and the corresponding position of device 300 asdetermined by dead reckoning position module 316. This recordedobservation data and corresponding position can be stored or marked indata store 320 in a manner to indicate that the recorded observationdata and corresponding position is based on a determined position ofdevice 300 that does not have an acceptable estimated accuracy. In oneor more embodiments, data transfer module 318 does not send to a dataservice the recorded observation data and corresponding position basedon a position of device 300 that does not have an acceptable estimatedaccuracy.

Subsequently, when a position of device 300 is determined that does havean acceptable estimated accuracy, backtracking module 312 compares thatposition with the acceptable estimated accuracy to the recordedpositions, and modifies at least some of the recorded positions. Theposition of device 300 that does have an acceptable estimated accuracycan be obtained in various manners, such as from a beacon at the edge ofa dead zone or within a dead zone, from GNSS module 302, and so forth.The modified recorded positions and corresponding observation data cansubsequently be stored or marked to no longer indicate they are based ona determined position of device 300 that does not have an acceptableestimated accuracy, and thus can be sent to a data service by datatransfer module 318.

Alternatively, rather than recording the observation data andcorresponding position of device 300, data collection module 310 canrecord the data collected by inertial sensor module 308 when neitherGNSS module 302 nor dead reckoning position module 316 determine aposition of device 300 with an acceptable estimated accuracy.Subsequently, when a position of device 300 can be determined that doeshave an acceptable estimated accuracy, backtracking module 312 can usethe recorded data from inertial sensor module 308 to perform thebacktracking. Thus, when neither GNSS module 302 nor dead reckoningposition module 316 can determine a position of device 300 with anacceptable estimated accuracy, a position of device 300 need not bedetermined until a position with an acceptable estimated accuracy can bedetermined.

In one or more embodiments, backtracking module 312 backtracks from theposition that does have an acceptable estimated accuracy for the deadreckoning fidelity interval. In one or more embodiments, backtrackingmodule 312 performs backtracking by starting at the position that has anacceptable estimated accuracy. Module 312 then works backwards throughthe inertial sensor data collected by inertial sensor module 308 andrecorded in data store 320 that leads up to that position, providing theinertial sensor data recorded in data store 320 (starting at theposition that has the acceptable estimated accuracy, so the data isprovided in the opposite order in which it was collected by inertialsensor module 308) to dead reckoning position module 316. Module 316determines a position of device 300 based on the inertial sensor dataprovided by backtracking module 312 as discussed above. Module 312 thuseffectively treats the device as moving backwards (e.g., until thedetermined position of device 300 does not have an acceptable estimatedaccuracy) based on the collected inertial sensor data.

Backtracking module 312 can perform the backtracking using a variety ofdifferent conventional and/or proprietary algorithms, rules, criteria,and so forth. For example, backtracking module 312 can modify thepositions for the dead reckoning fidelity interval to followapproximately the same path shape as was recorded by data collectionmodule 310, except backtracking starting at the position that has theacceptable estimated accuracy rather than the recorded position.

FIG. 6 illustrates an example use of backtracking in accordance with oneor more embodiments. A dead zone 602 is illustrated in FIG. 6, analogousto dead zone 502 of FIG. 5 or dead zone 402 of FIG. 4, although withoutan open area analogous to open area 510 of FIG. 5 or open area 410 ofFIG. 4. Multiple beacons 604, 606, and 608 are illustrated, analogous tobeacons 520-528 of FIG. 5.

A path 612 is included in FIG. 6, illustrating a path of a device as thedevice enters dead zone 602. Dead reckoning (e.g., dead reckoningposition module 316 of FIG. 3) is used to determine positions of thedevice for a dead reckoning fidelity interval, which lasts until a point614. At point 614, the position determined by dead reckoning no longerhas an acceptable estimated accuracy. However, dead reckoning continuesto be performed, identifying positions indicating a path 616. Positionsand corresponding observation data continue to be recorded along path616. In response to receiving a signal from beacon 606, a module of thedevice (e.g., position determination module 314 of FIG. 3) detects thatthe position of the device as determined based on the signal from beacon606 is not the same position as the position determined by deadreckoning (along path 616). Accordingly, a backtracking module (e.g.,module 312 of FIG. 3) modifies the recorded positions to reflect a path618 rather than path 616. These positions along paths 612 and 618, andcorresponding observation data can be sent to a data service (e.g., bydata transfer module 318 of FIG. 3).

Alternatively, rather than recording positions and correspondingobservation data along path 616, observation data that would result inpositions indicating path 616 is recorded (corresponding positions neednot be identified). In response to receiving a signal from beacon 606(which provides a position with an acceptable estimated accuracy), abacktracking module (e.g., module 312 of FIG. 3) works backwards throughthe recorded observation data to identify the path 618.

Returning to FIG. 3, in one or more embodiments inertial sensor module308 is deactivated or powered down (e.g., in response to a signal fromposition determination module 314) when device 300 is not within a deadzone. Inertial sensor module 308 is then activated or powered on inresponse to device 300 being detected as being at one of one or moreanchor locations. Inertial sensor module 308 can remain activated orpowered on until device 300 is no longer detected as being within thedead zone or at an anchor location, at which time inertial sensor module308 is deactivated or powered down. When device 300 is no longer withina dead zone can be detected in different manners, such as based onwhether GNSS module 302 provides a position of device 300 that has anacceptable estimated accuracy, in response to detecting another anchorlocation while in or having just been in a dead zone (e.g., an anchorlocation that indicates device 300 is leaving the dead zone), and soforth. Positions of device 300 are then determined as the positiondetected by GNSS module 302 as discussed above. A delay time (e.g., aparticular number of seconds or minutes) can optionally be implementedso that inertial sensor module 308 is not deactivated or powered downuntil a threshold amount of time (the delay amount of time) has elapsedafter device 300 is no longer detected as being within the dead zone orat an anchor location (and device 300 is still detected as not beingwithin the dead zone or at an anchor location when the threshold amountof time elapses). Various other factors can also be used to determinewhen to deactivate or power down inertial sensor module 308, such aswhether GNSS module 302 provides a position of device 300 that has anacceptable estimated accuracy.

Alternatively, inertial sensor module 308 can be deactivated or powereddown after the dead reckoning fidelity interval has elapsed. Inertialsensor module 308 can optionally be again powered on or activated inresponse to different events, such as receiving a signal received from abeacon, detecting that the device is again at an anchor location, and soforth.

In one or more embodiments, GNSS module 302 is deactivated or powereddown (e.g., in response to a signal from position determination module314) when device 300 is within a dead zone. GNSS module 302 can then beactivated or powered on (e.g., in response to a signal from positiondetermination module 314) when device 300 is no longer within the deadzone (e.g., as determined by the position of device 300 using deadreckoning, as determined by detecting device 300 is at one of one ormore anchor locations, and so forth). Alternatively, rather than beingdeactivated or powered down, GNSS module 302 can be configured (e.g., inresponse to a signal from position determination module 314) todetermine the position of device 300 at larger intervals when device 300is within a dead zone than when device 300 is not within a dead zone.For example, position determination module 314 can indicate to GNSSmodule 302 to determine the position of device 300 every 1 second whendevice 300 is not within a dead zone, and every 10 seconds when device300 is within a dead zone.

FIG. 7 is a flowchart illustrating an example process 700 for crowdsourcing based on dead reckoning in accordance with one or moreembodiments. Process 700 is carried out by a device, such as device 102of FIG. 1 or device 300 of FIG. 3, and can be implemented in software,firmware, hardware, or combinations thereof. Process 700 is shown as aset of acts and is not limited to the order shown for performing theoperations of the various acts. Process 700 is an example process forcrowd sourcing based on dead reckoning; additional discussions of crowdsourcing based on dead reckoning are included herein with reference todifferent figures.

In process 700, the device is identified as being at an anchor location(act 702). An anchor location can be identified in different manners,such as a location within a proximity zone along an edge of a dead zoneor a location where a signal from a beacon is detected as discussedabove.

Recording crowd sourcing data based on dead reckoning starts in responseto the device being at the anchor location (act 704). The starting ofrecording crowd sourcing data can include powering on or activating oneor more inertial sensors from which data is collected for deadreckoning.

Crowd sourcing data based on dead reckoning is recorded (act 706). Thisdata is recorded by the device implementing process 700 and can be sentto a crowd sourcing data service at a subsequent time, as discussedabove.

Recording crowd sourcing data based on dead reckoning includesidentifying one or more signal received at the device implementingprocess 700 while the device is at a particular position (act 708), andrecording both an indication of the position and an indication of theone or more signals received while the device is at that position (act710). The signals received can be Wi-Fi and/or cell transceiver signalsas discussed above, and the indication of the one or more signals caninclude an identifier of a network, access point, or transceiver, aswell as strengths of received signals, as discussed above. The positionis determined using dead reckoning, as discussed above. Acts 708 and 710are repeated for each of multiple different positions.

FIG. 8 is a flowchart illustrating an example process 800 for activatingand deactivating inertial sensors for dead reckoning in accordance withone or more embodiments. Process 800 is carried out by a device, such asdevice 102 of FIG. 1 or device 300 of FIG. 3, and can be implemented insoftware, firmware, hardware, or combinations thereof. Process 800 isshown as a set of acts and is not limited to the order shown forperforming the operations of the various acts. Process 800 is an exampleprocess for activating and deactivating inertial sensors for deadreckoning; additional discussions of activating and deactivatinginertial sensors for dead reckoning are included herein with referenceto different figures.

In process 800, the device is identified as being at an anchor location(act 802). An anchor location can be identified in different manners,such as a location within a proximity zone along an edge of a dead zoneor a location where a signal from a beacon is detected as discussedabove.

A determination is made, based at least in part on the device being atthe anchor location, whether and/or when to activate and/or deactivateone or more inertial sensors (act 804). This determination can be basedon various factors, such as whether the inertial sensors are alreadyactivated or deactivated, whether the device has moved away from ananchor location for which a determination in act 804 has been made, howlong the inertial sensors have been activated, and so forth. Forexample, the determination can be made in act 804 to activate one ormore inertial sensors if the inertial sensors are currently deactivatedand the device is identified as being at the anchor location. By way ofanother example, the determination can be made in act 804 to deactivateone or more inertial sensors a particular amount of time (e.g., a deadreckoning fidelity interval) after the device is identified as being atthe anchor location. By way of yet another example, the determinationcan be made in act 804 to deactivate one or more inertial sensors if theinertial sensors are currently activated and the device is identified asbeing at the anchor location.

In response to a determination being made to activate the inertialsensors, one or more inertial sensors are activated (act 806). Data iscollected from the one or more inertial sensors and used to determine adevice position using dead reckoning (act 808). Both an indication ofthe determined position and an identification of one or more signalsreceived while the device is at that position can be recorded asdiscussed above.

In response to a determination being made to deactivate the inertialsensors, one or more inertial sensors are deactivated (act 810). Theinertial sensors can be deactivated shortly after the determination ismade in act 804 (e.g., within 1 second), or alternatively after delayoccurs (e.g., a particular amount of time elapses, the deviceimplementing process 800 moves a particular distance, and so forth).

The activating and deactivating of sensors for dead reckoning techniquesdiscussed herein support various usage scenarios. For example, a usercan carry a device with him or her and that device can repeatedly recordthe position of the device and corresponding Wi-Fi and cell transceiversignals (and signal strengths) received at that position. While the useris outside and the device can receive signals from GNSS satellites, aGNSS module of the device is used to determine the position of thedevice. When the user walks into a dead zone (e.g., near a building,such as a mall) and the device can no longer receive signals from GNSSsatellites, the position of the device is determined using deadreckoning. Thus, the user's device is able to record data regarding thepositions of the device and corresponding Wi-Fi and cell transceiversignals (and signal strengths) received at those positions within thedead zone, even though signals from GNSS satellites are not received.This recorded data can be provided by the device to a crowd sourcingdata service, making information regarding Wi-Fi and cell transceiversignals and signal strengths received at positions at which signals fromGNSS satellites are not received available to the crowd sourcing dataservice. When the user subsequently exits the dead zone (e.g., leavesthe building), the device can resume using the GNSS module to determinethe position of the device.

By way of another example, a user can carry a device with him or her andthat device can repeatedly record the position of the device andcorresponding Wi-Fi and cell transceiver signals (and signal strengths)received at that position. While the user is outside and the device canreceive signals from GNSS satellites, a GNSS module of the device isused to determine the position of the device and inertial sensors of thedevice are not activated to conserve energy. When the user walks near adead zone (e.g., inside a building, such as a mall), the inertialsensors of the device are activated to allow positions of the device tobe determined using dead reckoning. If the user walks into the deadzone, the position of the device is determined using dead reckoning.However, if the user walks away from the dead zone, the inertial sensorscan be deactivated, and the position of the device continues to bedetermined by the GNSS module.

Various actions such as communicating, receiving, sending, recording,storing, obtaining, and so forth performed by various modules arediscussed herein. A particular module discussed herein as performing anaction includes that particular module itself performing the action, oralternatively that particular module invoking or otherwise accessinganother component or module that performs the action (or performs theaction in conjunction with that particular module). Thus, a particularmodule performing an action includes that particular module itselfperforming the action and/or another module invoked or otherwiseaccessed by that particular module performing the action.

FIG. 9 illustrates an example computing device 900 that can beconfigured to implement the activating and deactivating of sensors fordead reckoning in accordance with one or more embodiments. Computingdevice 900 can, for example, be a computing device 102 of FIG. 1,implement at least part of crowd sourcing data service 104 of FIG. 1, bea device 300 of FIG. 3, and so forth.

Computing device 900 includes one or more processors or processing units902, one or more computer readable media 904 which can include one ormore memory and/or storage components 906, one or more input/output(I/O) devices 908, and a bus 910 that allows the various components anddevices to communicate with one another. Computer readable media 904and/or one or more I/O devices 908 can be included as part of, oralternatively may be coupled to, computing device 900. Bus 910represents one or more of several types of bus structures, including amemory bus or memory controller, a peripheral bus, an acceleratedgraphics port, a processor or local bus, and so forth using a variety ofdifferent bus architectures. Bus 910 can include wired and/or wirelessbuses.

Memory/storage component 906 represents one or more computer storagemedia. Component 906 can include volatile media (such as random accessmemory (RAM)) and/or nonvolatile media (such as read only memory (ROM),Flash memory, optical disks, magnetic disks, and so forth). Component906 can include fixed media (e.g., RAM, ROM, a fixed hard drive, etc.)as well as removable media (e.g., a Flash memory drive, a removable harddrive, an optical disk, and so forth).

The techniques discussed herein can be implemented in software, withinstructions being executed by one or more processing units 902. It isto be appreciated that different instructions can be stored in differentcomponents of computing device 900, such as in a processing unit 902, invarious cache memories of a processing unit 902, in other cache memoriesof device 900 (not shown), on other computer readable media, and soforth. Additionally, it is to be appreciated that where instructions arestored in computing device 900 can change over time.

One or more input/output devices 908 allow a user to enter commands andinformation to computing device 900, and also allow information to bepresented to the user and/or other components or devices. Examples ofinput devices include a keyboard, a cursor control device (e.g., amouse), a microphone, a scanner, and so forth. Examples of outputdevices include a display device (e.g., a monitor or projector),speakers, a printer, a network card, and so forth.

Various techniques may be described herein in the general context ofsoftware or program modules. Generally, software includes routines,programs, applications, objects, components, data structures, and soforth that perform particular tasks or implement particular abstractdata types. An implementation of these modules and techniques may bestored on or transmitted across some form of computer readable media.Computer readable media can be any available medium or media that can beaccessed by a computing device. By way of example, and not limitation,computer readable media may comprise “computer storage media” and“communication media.”

“Computer storage media” include volatile and non-volatile, removableand non-removable media implemented in any method or technology forstorage of information such as computer readable instructions, datastructures, program modules, or other data. Computer storage mediainclude, but are not limited to, RAM, ROM, EEPROM, flash memory or othermemory technology, CD-ROM, digital versatile disks (DVD) or otheroptical storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or any other medium which canbe used to store the desired information and which can be accessed by acomputer. Computer storage media refer to media for storage ofinformation in contrast to mere signal transmission, carrier waves, orsignals per se. Thus, computer storage media refers to non-signalbearing media, and is not communication media.

“Communication media” typically embody computer readable instructions,data structures, program modules, or other data in a modulated datasignal, such as carrier wave or other transport mechanism. Communicationmedia also include any information delivery media. The term “modulateddata signal” means a signal that has one or more of its characteristicsset or changed in such a manner as to encode information in the signal.By way of example, and not limitation, communication media include wiredmedia such as a wired network or direct-wired connection, and wirelessmedia such as acoustic, RF, infrared, and other wireless media.Combinations of any of the above are also included within the scope ofcommunication media.

Generally, any of the functions or techniques described herein can beimplemented using software, firmware, hardware (e.g., fixed logiccircuitry), manual processing, or a combination of theseimplementations. The terms “module” and “component” as used hereingenerally represent software, firmware, hardware, or combinationsthereof. In the case of a software implementation, the module orcomponent represents program code that performs specified tasks whenexecuted on a processor (e.g., CPU or CPUs). The program code can bestored in one or more computer readable memory devices, furtherdescription of which may be found with reference to FIG. 9. In the caseof hardware implementation, the module or component represents afunctional block or other hardware that performs specified tasks. Forexample, in a hardware implementation the module or component can be anapplication-specific integrated circuit (ASIC), field-programmable gatearray (FPGA), complex programmable logic device (CPLD), and so forth.The features of the activating and deactivating of sensors for deadreckoning techniques described herein are platform-independent, meaningthat the techniques can be implemented on a variety of commercialcomputing platforms having a variety of processors.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

1. A method comprising: identifying, in a device, that the device is atan anchor location; activating, in response to the device being at theanchor location, one or more inertial sensors; and collecting data fromthe one or more inertial sensors to determine a position of the deviceusing dead reckoning.
 2. A method as recited in claim 1, the anchorlocation comprising a proximity zone along an edge of a dead zone.
 3. Amethod as recited in claim 1, the anchor location comprising a locationwhere a signal from a beacon is detected.
 4. A method as recited inclaim 1, the one or more inertial sensors being included as part of thedevice.
 5. A method as recited in claim 1, further comprisingdeactivating the one or more inertial sensors in response to the deadreckoning not providing an acceptable estimated accuracy of the positionof the device.
 6. A method as recited in claim 1, further comprisingdeactivating the one or more inertial sensors in response to both thedevice no longer being at the anchor location and a global navigationsatellite system of the device providing an acceptable estimatedaccuracy of the position of the device.
 7. A method as recited in claim1, further comprising deactivating the one or more inertial sensors athreshold amount of time after determining that the device is no longerwithin a dead zone.
 8. A method as recited in claim 1, furthercomprising deactivating the one or more inertial sensors, then againactivating the one or more inertial sensors in response to receiving asignal from a beacon.
 9. A method as recited in claim 8, the beaconcomprising a beacon in a dead zone.
 10. A method comprising:identifying, in a device, that the device is at an anchor location; anddetermining, based at least in part on the device being at the anchorlocation, when to deactivate one or more inertial sensors from whichdata is collected to determine the position of the device using deadreckoning.
 11. A method as recited in claim 10, the anchor locationcomprising a proximity zone along an edge of a dead zone.
 12. A methodas recited in claim 10, the anchor location comprising a location wherea signal from a beacon is detected.
 13. A method as recited in claim 10,the one or more inertial sensors being included as part of the device.14. A method as recited in claim 13, each of the one or more inertialsensors detecting movement and/or direction of the device.
 15. A methodas recited in claim 10, the determining comprising determining todeactivate the one or more inertial sensors in response to the deadreckoning not providing an acceptable estimated accuracy of the positionof the device.
 16. A method as recited in claim 10, the determiningcomprising determining to deactivate the one or more inertial sensors inresponse to both the device no longer being at the anchor location and aglobal navigation satellite system of the device providing an acceptableestimated accuracy of the position of the device.
 17. A method asrecited in claim 10, the determining comprising determining todeactivate the one or more inertial sensors a threshold amount of timeafter determining that the device is no longer within a dead zone.
 18. Amethod as recited in claim 10, further comprising activating the one ormore inertial sensors in response to receiving a signal from a beacon.19. A method as recited in claim 18, the beacon comprising a beacon in adead zone.
 20. One or more computer storage media having stored thereonmultiple instructions that, when executed by one or more processors of adevice, cause the one or more processors to: identify, in the device,that the device is at a first anchor location, the first anchor locationbeing a proximity zone along an edge of a dead zone or a location wherea signal from a beacon is detected; activate, in response to the devicebeing at the first anchor location, one or more inertial sensors;collect data from the one or more inertial sensors to determine aposition of the device using dead reckoning; identify, in the device,when the device is at a second anchor location, the second anchorlocation being a proximity zone along an edge of a dead zone or alocation where a signal from a beacon is detected; and determine, basedat least in part on whether the device is at the second anchor location,when to deactivate one or more inertial sensors.